Gai would demolish Kisame, though Kakashi won't beat Obito. (Rinnegan) So Gai demolishes Kisame like he did in canon, and then goes to help Kakashi defeat Obito.
He didn't specify which Obito. So 6 Bijuu gg
So I'm going to assume it's an Obito who doesn't need Kabuto's help to use an ability. Thus no Bijuu. Only Mazo. So The Masters win. Mid difficulty. Maybe mid-high.
Why would you pick Kisame....who gets wrecked by Gai
Wait so Gai and MS Kakashi can take out the Gedo Mazo? Kamui is completely useless as Obito can easily take it out. Gedo Mazo tanks Hirudora effortlessly. But then again you think the Gedo can be one shotted by a Rasenshuriken.
Yes you did sir.
Although Obito couldn't ask for a more loyal one.........Meh, kisame isn't a great teammate for obito..